Bush__The_Essential_Physics_for_Medical_Imaging - Biomedical ...

ination should remove their protective clothing and be surveyed with a GM surveyinstrument to assure that they are not contaminated. If the spill involves volatileradionuclides or if other conditions exist that suggest the potential for internal contamination,bioassays should be performed by the radiation safety staff. Commonbioassays for internal contamination include external counting with aNal (TI)detector (e.g., thyroid bioassay for radioiodine) and radioactivity measurement ofurine (e.g., tritium bioassay).Sometimes nuclear medicine patients are administered the wrong radiopharmaceuticalor the wrong activity. These accidents are called medical events or misadministrations.The following event has occurred at a several institutions: a patientreferred for a whole-body bone scan [740 MBq (20 mCi) ofTc-99m MOP] hasbeen mistakenly administered up to 370 MBq (10 mCi) ofI-131 sodium iodide fora whole-body thyroid cancer survey [thyroidal dose for 370 MBq and 20% uptakeis ~100 Gy (10,000 rad)]. The cause has often been a verbal miscommunication. Inanother case, a mother who was nursing an infant was administered a therapeuticdose of 1-131 sodium iodide without being instructed to discontinue breast-feeding,resulting in an estimated dose of 300 Gy (30,000 rad) to the infant's thyroid.The following precautions, most of which are mandated by the U.S. Nuclear RegulatoryCommission (NRC), are intended to reduce the frequency of such incidents.The vial radiation shield containing the radiopharmaceutical vial must be conspicuouslylabeled with the name of the radiopharmaceutical or its abbreviation.Each syringe containing a dosage of a radiopharmaceutical must be conspicuouslylabeled with the patient's name and the radiopharmaceutical (or its abbreviation).The patient's identity must be verified, whenever possible by two means (e.g., byhaving the patient recite his or her name and social security number). The possibilitythat a woman is pregnant or breast-feeding must be ascertained before administeringthe radiopharmaceutical. In the case of activities of 1-131 sodium iodideexceeding 30 IlCi and therapeutic radiopharmaceuticals, pregnancy should be ruledout by a pregnancy test, certain premenarche in a child, certain postmenopausalstate, or documented hysterectomy or tubal ligation.Before the administration of activities exceeding 1.1 MBq (30 IlCi) of 1-131 inthe form of sodium iodide and any radionuclide therapy, a written directive mustbe prepared by the nuclear medicine physician identifYing the patient, the radionuclide,the radiopharmaceutical, the activity to be administered, and the route ofadministration. The written directive must be consulted at the time of administrationand the patient's identity should be verified by two methods. Although notrequired by the NRC, similar precautions should be taken when reinjecting autologousradiolabeled blood products to prevent transfusion reactions and the transmissionof pathogens.Women who are nursing infants by breast at the time of the examinationshould be counseled to discontinue breast-feeding until the radioactivity in thebreast milk has been reduced to a safe level. Table 23-17 contains recommendationsfor cessation of breast-feeding after the administration of radiopharmaceuticals tomothers. The NRC requires written instructions to nursing mothers if total effectivedose equivalent to a nursing infant could exceed 1 mSv (100 mrem) (Code of